The bind with the **fire batteries is that they rarely are anywhere near the claimed capacity. At least sometimes they are 're-claimed' from previously used battery packs.
The rub comes when you use several of them together, or mixed with other cells. Since the **Fire brands are generally much lower than claimed capacity, when you mix them with quality cells that actually are somewhere near the rated capacity, it is very easy to over discharge the **Fire Cell(s), and that is bad news.Bad things can happen after a cell has been discharged below ~2.8 volts (some are designed to go down to 2.5 volts). If you have protected cells, the protection should disconnect the cell to prevent overdischarge. If they aren't protected, there is nothing to stop you from overdischarging them. Really bad things can happen if you attempt to recharge a Li-Ion cells that has been discharged below its lower limit. The money you can save by using **fire cells is peanuts compared to the damage they can do. It is probably OK to use these cells in lights that use a single cell, but understand that run time may be less (Usually a lot less), than a real 3400mAh cell.
